To demonstrate classical conditioning in the planarian in a situation uncontaminated by the possible artifacts of pseudoconditioning or sensitization 30 Phagocata gracilis were successfully trained, by the use of directional shock as the unconditioned stimulus, to turn in one direction to a light, and in the opposite direction to vibration. Ten similarly trained planaria tested by an independent observer who did not know the previous training conditions experienced by any animal showed similar results.